Structurally coated silica

ABSTRACT

A structurally coated silica can be prepared by spraying and mixing a pyrogenic silica with water and a coating agent in a suitable mixing vessel, then milling and then conditioning the product.  
     The structurally coated silica can be used as a matting agent in lacquers.

[0001] This application claims the benefit of U.S. ProvisionalApplication No. 60/433,963, filed Dec. 18, 2002.

[0002] The invention provides a structurally coated silica, a processfor its preparation and its use.

[0003] An aerogel-like structured silica is disclosed in DE 24 14 478.This silica is prepared by incorporating and uniformly distributingwater in an air-dispersed pyrogenic silica and drying the powderymixture obtained.

[0004] This silica has the disadvantage that it has a strong tendency tosettle out and is impossible or very difficult to redisperse.

[0005] The document DE 15 92 863 describes organically modifiedprecipitation silicas which are coated, for example, with a wax and maybe used as matting agents.

[0006] These known silicas exhibit poor transparency in a variety oflacquer systems. Due to the high moisture content, these silicas cannotbe used in moisture-curing polyurethane systems. Lacquer systems whichare difficult to provide with a matt finish, such as polyurethane andepoxy lacquer systems, cannot be matted in a satisfactory manner usingknown silicas.

[0007] Thus, there is the object of preparing a silica which does nothave these disadvantages.

[0008] The invention provides a structurally coated silica. It may havea carbon content of 1 to 30 wt. %.

[0009] The silica according to the invention may have a BET surface areaof 80 to 450 m²/g. It may have a compacted bulk density of 10 to 100g/l. The DBP index may be 200 to 150.

[0010] A 4% strength aqueous suspension of the silica according to theinvention may have a pH of 6 to 8.

[0011] The expression structurally coated means that the end product ismore highly structured than the starting product and is also coated. Thestructurally coated silica has a higher DBP index than the initialsilica.

[0012] The structurally coated silica according to the invention may beprepared by spraying and mixing a pyrogenic silica with water and acoating agent in a suitable mixing vessel, then milling and subsequentlydrying.

[0013] Any known pyrogenic silica may be used as the pyrogenic silica.

[0014] In a preferred embodiment of the invention, pyrogenic silicas inaccordance with Table 1 may be used.

[0015] Pyrogenic silicas are disclosed in Ullmann's Encyklopädie dertechnischen Chemie, 4th edition, vol. 21, pages 464 et seq. (1982).

[0016] They are prepared by flame hydrolysis, when a vaporizable metalor metalloid compound, such as for example silicon tetrachloride, isburnt with hydrogen- and oxygen-containing gases in a flame. TABLE 1Physico-chemical data for AEROSILS AEROSIL AEROSIL AEROSIL AEROSILAEROSIL AEROSIL AEROSIL AEROSIL Test method 90 130 150 200 300 380 OX 50TT 600 Behaviour in hydrophilic presence of water Appearance fluffywhite powder BET surface m²/g 90 ± 15 130 ± 25 150 ± 15 200 ± 25 300 ±30 380 ± 30 50 ± 15 200 ± 50 area¹⁾ Average size nm 20 16 14 12 7 7 4040 of primary particles Bulk density g/l 80 50 50 50 50 50 130 60approx. value²⁾ g/l 120 120 120 120 120 120 compacted g/l 50/75 50/7550/75 goods g/l 120 120 (additive “V”) VV goods (additive “VV”)¹²⁾ Losson % <1.0 <1.5 <0.5⁹⁾ <1.5 <1.5 <2.0 <1.5 <2.5 drying³⁾ (2 hours at 105°C.) on dispatch from delivery factory Loss on % <1 <1 <1 <1 <2 <2.5 <1<2.5 ignition⁴⁾ ⁷⁾ (2 hours at 1000° C.) pH⁵⁾ 3.7-4.7 3.7-4.7 3.7-4.73.7-4.7 3.7-4.7 3.7-4.7 3.8-4.8 3.6-4.5 SiO₂ ⁸⁾% >99.8 >99.8 >99.8 >99.8 >99.8 >99.8 >99.8 >99.8 Al₂O₃ ⁸⁾ % <0.05 <0.05<0.05 <0.05 <0.05 <0.05 <0.08 <0.05 Fe₂O₃ ⁸⁾ % <0.003 <0.003 <0.003<0.003 <0.003 <0.003 <0.01 <0.003 TiO₂ ⁸⁾ % <0.03 <0.03 <0.03 <0.03<0.03 <0.03 <0.03 <0.03 HCI⁸⁾ ¹⁰⁾ % <0.025 <0.025 <0.025 <0.025 <0.025<0.025 <0.025 <0.025 Screening % <0.05 <0.05 <0.05 <0.05 <0.05 <0.05<0.2 <0.05 residue⁸⁾ (Mocker, 45 μm) Drum size kg 10 10 10 10 10 10 1010 (nett)¹¹⁾

[0017] From among the pyrogenic silicas listed in Table 1, non-compactedvariants of preferably all the types of Aerosil, with the exception ofAEROSIL OX50, may also be used.

[0018] Waxes and/or organically modified polysiloxanes in the form ofaqueous dispersions or emulsions may be used as coating agents. Aqueousdispersions or emulsions of waxes for use according to the invention maycontain the following waxes:

[0019] Polyethylene homopolymer and copolymer waxes; number averagemolecular weight 700-10,000 g/mol, with a dropping point of 80-140° C.

[0020] PTFE waxes; polytetrafluoroethylene with a molecular weightbetween 30,000 and 2,000,000 g/mol, in particular between 100,000 and1,000,000 g/mol.

[0021] Polypropylene homopolymer and copolymer waxes; number averagemolecular weight 700-10,000 g/mol, with a dropping point of 80-160° C.

[0022] Amide waxes; prepared by reacting ammonia or ethylenediamine withsaturated and unsaturated fatty acids. The fatty acids are, for example,stearic acid, tallow fatty acid, palmitic acid or erucic acid.

[0023] FT paraffins; number average molecular weight 400-800 g/mol, witha dropping point of 80-125° C.

[0024] Montan waxes including acid and ester waxes with a carboxylicacid carbon-chain length of C₂₂-C₃₆. The ester waxes are reactionproducts of Montan wax with one or more polyhydric alcohols such as, forexample, ethanediol, butane-1,3-diol or propane-1,2,3-triol.

[0025] Natural waxes such as, for example, carnauba wax or candelillawax.

[0026] Macro- or microcrystalline paraffins which are produced duringthe refining of petroleum. The dropping point of the paraffins isbetween 45 and 65° C., that of the microcrystalline waxes is between 73and 100° C.

[0027] Sorbitan esters of Montan alcohols.

[0028] Furthermore, the following may be used:

[0029] A homopolymer or copolymer of C₂-C₁₈-α-olefins prepared usingZiegler metal catalysis and one or more other waxes as auxiliary agents,chosen from the group:

[0030] PE waxes,

[0031] PTFE waxes,

[0032] PP waxes,

[0033] amide waxes,

[0034] FT paraffins,

[0035] Montan waxes,

[0036] natural waxes,

[0037] macro- and microcrystalline paraffins,

[0038] polar polyolefin waxes or

[0039] sorbitan esters

[0040] The homopolymers or copolymers of C₂-C₁₈-α-olefins prepared usingZiegler metallocene catalysis preferably have the following properties:

[0041] Dropping point (Dp): 80-165° C. 90-155° C.

[0042] Acid value (AV): 0-50 mg KOH/g

[0043] Density: 0.87-1.03 g/cm³

[0044] Viscosity of melt at 170° C.: 10-100,000 mPas

[0045] Suitable polyolefin waxes are homopolymers of ethylene orpropylene or copolymers of. ethylene and propylene with each other orwith one or more 1-olefins.

[0046] Polysiloxanes for use according to the invention may be:

[0047] An oil-in-water emulsion of

[0048] organically modified polysiloxanes (organic modification: C₂ toC₈ alcohols and EO/PO polyethers)

[0049] approximate average Mw: 1000 to 5000 g/mol

[0050] (filled with hydrophobic silica) active substance content ofemulsion: about 20%

[0051] Since the volume of the silica decreases only very slightly whenincorporating water and the coating agent, it is assumed that theassociation of primary particles originally present in air-dispersedpyrogenic silica is substantially retained. As a result of loading withwater and coating agent, partial dissolution of the surface of thesilica probably takes place so that dissolved silica is present here.This binds the primary particles together at any contact points duringthe subsequent drying process.

[0052] Thus a dispersion-stable substance with high macrovolumes andvery low apparent density (bulk density), corresponding to a KistlerAerogel, is produced from a pyrogenic silica by targeted loading withwater and coating agent followed by drying.

[0053] Furthermore, it has been found that the structure which isapparently present prior to incorporating water and the coating agent,determined by the packing density of the pyrogenic silica in air andwhich is expressed by its apparent density (bulk density), has anobvious effect on the product produced by the process according to theinvention: The more voluminous the starting product, the more voluminousthe end product obtained.

[0054] It has proven expedient to use pyrogenic silicas with a compactedbulk density of 10 to 130, preferably 15 to 80, in particular about 20g/l, to prepare products according to the invention.

[0055] In addition, it has proven advantageous to choose pyrogenicsilicas with large surface areas and thus small primary particles.According to a beneficial embodiment of the process according to theinvention, silicas with BET surface areas between 100 and 480, inparticular 250 to 410 m²/g are used.

[0056] Complete wetting of the primary particles can be achieved when 5to 20, in particular 7 to 15 wt. % of water and coating agent areincorporated and uniformly distributed in the silica. Since the waterwhich has been incorporated is to be dried out again, the smallestpossible amount of water is aimed at, for economic reasons. However, theamount required depends to some extent on the type of incorporationprocedure used.

[0057] The build up of a structure in accordance with the invention canbe greatly encouraged when basic compounds such as, for example,ammonia, sodium or potassium hydroxide, water-soluble amines,waterglass, etc. are added to the water and coating agent. The amountsadded are expediently chosen so that the pH in the water is adjusted toa value of 7 to 14, preferably 8 to 12, in particular 10 to 11.

[0058] The alkalis used act as solution promoters for silica and bringabout an increase in the macroporosity of the process products.

[0059] Instead of alkaline compounds, free silica or hydrolytic silicaand/or alkali-releasing substances can also be added to the water andcoating agent.

[0060] In fact free silica, produced for example by the acidification orion exchange of silicate solutions or by hydrolytic decomposition ofsilicon-organic compounds, for example of tetramethyl silicate, alsopromotes the build up of a structure. A hydrolytic alkali and silicareleasing substance is, for example, sodium methylsiliconate.

[0061] Uniform distribution of the water and coating agent in the silicacan take place by dripping or spraying these into/onto the silica whichis being mixed by agitation with the silica at temperatures between 20and 100, preferably 40 to 70, in particular 50 to 60° C. Mixing byagitation is expediently performed by stirring.

[0062] Another variant for introducing the water comprises spraying thesilica with water and coating agent in a fluidized stream of material,for example using a downpipe.

[0063] It has also proven advantageous to perform the water loadingprocess at a moderately elevated temperature. This can be achieved bypreheating either the water to be incorporated with the coating agent orthe silica or both components. Thus, the water to be incorporated withthe coating agent can have a temperature between 20 and 100, preferably50 to 100, in particular 90 to 100° C.

[0064] The build up of structure can also be promoted by short-termsteaming of the loaded silica in a sealed space. Steaming leads toespecially good distribution of the water. It has proven advantageoushere to steam the water-laden silica, before drying, in a sealed vesselfor about 5 to 60, preferably 10 to 30, in particular about 20 minutes,at temperatures up to the boiling point of water, preferably 50 to 80,in particular about 60° C.

[0065] Another possibility for improving the distribution of water andcoating agent comprises milling the silica laden with water and coatingagent, for example in pin mills or air-jet mills.

[0066] The silica is then dried, wherein the preformed structure isprobably fixed via the primary particles whose surface is covered withdissolved silica or coated with free silica.

[0067] The type of drying is less critical. The prepared mixture ofsilica and coating agent, which always appears to have the status of adry powder, can be dried, for example, in tray, disc, Büttner,continuous flow or microwave driers. The silica laden with water andcoating agent can, however, also be simultaneously milled and dried in asteam or air-jet mill in order to save a separate process step.

[0068] If a separate drying procedure is performed with the powderedmixture obtained after loading with water and coating agent, this may befollowed by dry milling in a pin mill or air-jet mill.

[0069] The silica according to the invention can be used as a mattingagent in lacquers. It then has the following advantages:

[0070] no settling out, or easy to redisperse,

[0071] no impairment to the matting efficiency,

[0072] improvement to the feel,

[0073] enables more highly transparent clear lacquers,

[0074] low moisture content, therefore can be used in moisture-curing PUsystems (polyurethane systems),

[0075] better rheology, because it is less thixotropic.

[0076] The silica according to the invention can be used in particularin polyurethane lacquers.

Examples

[0077] Preparing the Structurally Coated Silica According to theInvention

[0078] Hydrophilic pyrogenic silica (Aerosil 300) with the followingphysico-chemical properties is used: Specific BET surface area [m²/g]:290.0 pH: 4.2 Compacted density [g/l]: 35 Loss on drying [%]: 0.8 DBPindex [%]: 305.0 Carbon content [%]: 0

[0079] A plough bar mixer is used as the mixing vessel. The coatingagent is sprayed in at room temperature using a two-fluid nozzle.

[0080] The following products are used as coating agents:

[0081] Coating Agent A

[0082] Coating agent A is known from EP 0 341 383 A2. it is a waxemulsion and is prepared as follows:

[0083] The wax emulsion is prepared in an autoclave which can be heatedwith steam and is provided with a disperser. In this, 4.8 parts by wt.of an alkyl polyglycol ether (Marlowet® GFW) at 100° C. are firstdissolved in 81.0 parts by wt. of water at about 100° C. Then 14.2 partsby wt. of low-pressure polyethylene wax are added and the mixture isheated to 130° C. On reaching 130° C., the disperser is switched on andthe mixture is dispersed for 30 minutes. The temperature is held atbetween 130 and 140° C. for this period. After switching off thedisperser and cooling to about 110° C., the final emulsion isdischarged.

[0084] The polyethylene wax is characterized by the following physicalcharacteristics: average molecular weight 1000 solidification point100-104° C. dropping point 110-117° C. density (g/cm³) 0.93

[0085] The emulsion is then adjusted to the required pH.

[0086] Coating Agent B

[0087] Coating agent B is known from EP 0 341 383 A2. It is a waxemulsion and is prepared as follows:

[0088] The wax emulsion is prepared in an autoclave which can be heatedwith steam and which is provided with a disperser. In this, 4.8 parts bywt. of an alkyl polyglycol ether(Marlowet® GFW) at 100° C. are firstdissolved in 81.0 parts by wt. of water at about 100° C.

[0089] Then 14.2 parts by wt. of a low-pressure polyethylene wax areadded and the mixture is heated to 130° C. On reaching 130° C., thedisperser is switched on and the mixture is dispersed for 30 minutes.The temperature is held at between 130 and 140° C. during this period.After switching off the disperser and cooling to about 110° C., thefinal emulsion is discharged.

[0090] The polyethylene wax used is characterized by the followingcharacteristics: average molecular weight 2700 Solidification point 92-96° C. dropping point 102-110° C. density (g/cm³) 0.92

[0091] The emulsion is then adjusted to the required pH.

[0092] Coating Agent C

[0093] Coating agent C consists of 656.4 g of an aqueous polysiloxaneemulsion which is diluted with 210 g of water and adjusted to therequired pH.

[0094] The polysiloxane emulsion has the following physico-chemicalproperties: Form: viscous Color: white Odor: slight characteristic odorBoiling point: about 100° C. Density: about 1 g/cm³ at 20° C. Solubilityin water: miscible pH: 5.5 at 20° C. in original state viscosity,dynamic: about 2,300 mPa.s at 25° C.

[0095] Coating Agent D

[0096] Coating agent D consists of 503.0 g of an aqueous alkylester/polydimethylsiloxane emulsion which is diluted with 116 g of waterand adjusted to the required pH.

[0097] The alkyl ester/polydimethylsiloxane emulsion has the followingphysico-chemical properties: Form: viscous Color: white Odor: slightcharacteristic odor Boiling point: about 100° C. Density: about 0.95g/cm³ at 25° C. Solubility in water: miscible pH: 5.8 at 25° C. inoriginal state Viscosity, kinematic: about 40-120 mm²/s at 20° C.Method: 4 DIN 53211

[0098] Coating Agent E

[0099] Coating agent E consists of 365.6 g of an aqueous emulsion of anester wax and canauba wax and 346 g of water. The mixture is adjusted toa pH of 10.6.

[0100] The emulsion of ester wax, carnauba wax, emulsifier and water hasthe following composition: Components: %-age range CAS-No. Carnauba wax15-25%  8015-86-9 Ester wax 15-25% 73138-45-1 Emulsifier  5-10%68920-66-1 Water 40-50%  7732-18-5

[0101] The emulsion used has the following physico-chemical properties:Appearance: liquid Color: pale yellow to light brown Odor: mild Boilingpoint: 100° C., starts to boil Melting point: 0° C., like water (solidabout 86° C.) Relative density 1.01-1.02 g/ml at 20° C. (water = 1):Vapor pressure: 23 mbar (at 20° C.), same as water pH: 5.0-5.6Solubility in water: miscible in all ratios

[0102] Comparison Example

[0103] For comparison, only water (adjusted to be alkaline) instead ofcoating agent was used in example 8. TABLE 2 Preparing the moistenedmaterial Loss on Amount of drying of Amount of coating agent pH ofcoating pH adjusted moistened Number silica [kg] Coating agent [kg]agent by adding material 1 2 A 0.938 10.5 NaOH 27.6 2 2 B 0.995 10.5NH₄OH 27.4 3 2 C 0.865 11.3 NH₄OH 24.4 4 2 C 1.110 11.2 waterglass 27.45 2 D 0.634 9.8 waterglass 14.3 6 2 D 1.593 10.8 NaOH 21.4 7 2 E 0.71110.6 NH₄OH 14.6 8 2 none 0.765 11.5 NH₄OH 27.8 comparison example

[0104] TABLE 3 Milling and drying the moistened material ThroughputDrying during milling temperature Drying time Number Milling unit [kg/h][° C.] [h] 1 pin mill 5 120 15 2 gas-jet mill 7 120 15 3 gas-jet mill 7120 13 4 gas-jet mill 7 120 12 5 pin mill 5 120 12 6 pin mill 5 120 15 7pin mill 5 120 10 8 gas-jet mill 7 120 11

[0105] TABLE 4 Physico-chemical data Number LOD [%] LOI [%] pH DBP [%]CBD [g/l] C [%] Coating agent used 1 0.8 7.8 6.4 338 26 4.1 A 2 2.5 7.46.3 321 29 4.3 B 3 1.6 4.9 6.5 326 24 3.0 C 4 1.6 6.1 6.9 301 25 4.4 C 50.8 9.4 6.3 331 23 6.5 D 6 2.0 19.4 7.2 n.d. 46 16.0 D 7 2.7 8.6 7.4 31326 5.0 E 8 2.3 1.6 6.9 326 22 0 none comparison example

[0106] Determining the Physico-chemical Characteristics

[0107] BET Surface Area

[0108] The BET surface area is determined in accordance with DIN 66 131using nitrogen.

[0109] Compacted Density

[0110] The compacted density is determined using a method based on DINISO 787/XI

[0111] Basis for Determining Compacted Density

[0112] The compacted density (previously compacted volume) is given bythe quotient of the weight and the volume of the powder after compactingin a compacting volumeter under fixed conditions. According to DIN ISO787/XI the compacted density is given in g/cm³. Due to the very lowcompacted density of the oxides, however, we give the values in g/l.Furthermore, we do not perform drying and screening procedures nor do werepeat the compacting process.

[0113] Equipment for Determining the Compacted Density

[0114] Compacting volumeter

[0115] Measuring cylinder

[0116] Laboratory scales (readability 0.01 g)

[0117] Method for Determining the Compacted Density 200±10 ml of oxideare placed in the measuring cylinder of the compacting volumeter in sucha way that there are no cavities and the surface is horizontal.

[0118] The weight of the sample in the measuring cylinder is determinedaccurately to 0.01 g. The measuring cylinder with the sample is insertedinto the measuring cylinder holder in the compacting volumeter andrammed down 1250 times.

[0119] The volume of the compacted oxide is read off accurately to 1 ml.

[0120] Evaluating the Compacted Density Determination${{Compacted}\quad {density}\quad \left( {g\text{/}1} \right)} = \frac{g\quad {amount}\quad {weighed}\quad {out} \times 1000}{{ml}\quad {volume}\quad {read}\quad {off}}$

[0121] pH

[0122] The pH is determined in 4% strength aqueous solution; in the caseof hydrophobic oxides in water:methanol 1:1.

[0123] Reagents for Determining pH

[0124] distilled or deionized water, pH >5.5 Methanol, AR Buffersolutions pH 7.00 pH 4.66

[0125] Equipment for Determining pH

[0126] Laboratory scales, (readability 0.1 g)

[0127] Beaker, 250 ml

[0128] Magnetic stirrer

[0129] Magnetic rod, length 4 cm

[0130] Combined pH electrode

[0131] pH instrument

[0132] Dispensette, 100 ml

[0133] Instructions for Determining pH

[0134] The method for determining pH is based on DIN/ISO 787/IX:Calibration: Before measuring the pH, the instrument is calibrated withbuffer solutions. If several measurements are performed in sequence, asingle calibration procedure is sufficient.

[0135] 4 g of hydrophilic oxide are stirred with the aid of adispensette in a 250 ml beaker with 96 g (96 ml) of water and then forfive minutes with a magnetic stirrer (speed ca. 1000 min⁻¹) with the pHelectrode immersed therein.

[0136] 4 g of hydrophobic oxide are stirred up with 48 g (61 ml) ofmethanol in a 250 ml beaker and the suspension is diluted with 48 g (48ml) of water and stirred with a magnetic stirrer (speed ca. 1000 min⁻¹)for five minutes with the pH electrode immersed therein.

[0137] After switching off the stirrer, the pH is read off after awaiting time of one minute. The result is recorded to one decimal place.

[0138] Loss on Drying

[0139] Differently from the amount of 10 g initially weighed out, asmentioned in DIN ISO 787 II, a 1 g amount is used for determining theloss on drying.

[0140] The lid is put on before cooling. A second drying is notperformed.

[0141] About 1 g of the sample is weighed accurately to 0.1 mg into aweighing dish with a ground-glass lid and which has been dried at 105°C., avoiding the production of dust, and dried at 105° C. for two hoursin a drying cabinet. After cooling with the lid in place, in adesiccator over blue silica gel, the dish is reweighed.${\% \quad {loss}\quad {on}\quad {drying}\quad {at}\quad 105{^\circ}\quad {C.}} = {\frac{g\quad {loss}\quad {in}\quad {weight}}{g\quad {initial}\quad {{wt}.\quad {of}}\quad {sample}} \times 100}$

[0142] The result is recorded to one decimal place.

[0143] Loss on Ignition

[0144] Equipment for Determining Loss on Ignition

[0145] Porcelain crucible with crucible lid

[0146] Muffle furnace

[0147] Analytical scales (readability 0.1 mg)

[0148] Desiccator

[0149] Method Used to Determine Loss on Ignition

[0150] Differently from DIN 55 921, 0.3-1 g of the substance which hasnot been predried is weighed accurately to 0.1 mg into a previouslystrongly heated porcelain crucible with a crucible lid and heated for 2hours at 1000° C. in a muffle furnace.

[0151] Efforts must be made to avoid the production of dust. It hasproven beneficial to place the weighed out sample in a muffle furnacewhich is still cold.

[0152] Due to slow heating up of the furnace, vigorous air turbulence inthe porcelain crucible is avoided.

[0153] After reaching 1000° C., heating is continued for another 2hours. Then the crucible is covered with a lid, the crucible is placedin a desiccator over blue silica gel and the loss in weight isdetermined.

[0154] Evaluating the Loss on Ignition Determination

[0155] Since the loss on ignition is given with reference to the sampledried for 2 hours at 105° C., the following formula is used for thecalculation:${\% \quad {loss}\quad {on}\quad {ignition}} = {\frac{{m_{0} \times \frac{100 - {LOD}}{100}} - m_{1}}{m_{0} \times \frac{100 - {LOD}}{100}} \times 100}$

[0156] m₀=amount initially weighed out (g)

[0157] LOD=loss on drying (%) m₁=weight of strongly heated sample (g)

[0158] The result is recorded to one decimal place.

[0159] DBP Index

[0160] Equipment for Determining DBP Index

[0161] To-pan scales

[0162] Plastic beaker (250 ml)

[0163] Brabender plastograph with metering unit

[0164] Reagent

[0165] Dibutyl phthalate (techn.)

[0166] Method

[0167] 1. Check the cut-off point

[0168] Switch on the plastograph without the metering pump.

[0169] Open the protective valve for the operating section (under

[0170] Display)

[0171] Press the “Func” button; the display should alternate between thecut-off value “1000”and the alarm “AI H.A.”;

[0172] after 5 sec. the display again appears in Normal mode.

[0173] 2. Calibration

[0174] Switch on the plastograph without the metering pump.

[0175] Switch on the compounder (press both Start buttonssimultaneously).

[0176] Press the “Cal” button once, then press the “Funk” button; thedisplay should alternate between the current zero point and “Lo S.C.”.

[0177] Press the “Cal” button again; after four seconds (calibration),the instrument displays the current total range “10000”and “Fu S.C.”.

[0178] Press the “Cal” once more; after four seconds (calibration), theinstrument should display the friction-corrected zero point “tare”.

[0179] Press the “Cal” button once more and wait 5 sec.

[0180] If required, perform the “cut-off point” and “calibration”procedures once daily before taking measurements!

[0181] 3. Measurement

[0182] b 12.5 g of sample are weighed into a plastic beaker and placedin the compounding chamber. If instructed, the amount weighed out maydiffer from this (e.g. 8 or 20 g). The DBP metering unit is switched on.As soon as the filling procedure is complete (display F), theplastograph is ready for use.

[0183] Measurement starts when the Start buttons are pressedsimultaneously.

[0184] The metering unit meters 4 ml DBP/min until the pre-set cut-offpoint (1000) is reached.

[0185] The instrument switches off automatically.

[0186] Only the consumption of DBP can be read on the display for themetering unit.

[0187] Calculation${{DBP}\quad (\%)} = \frac{{Dosimat}\quad {display} \times 1.047 \times 100}{{Amount}\quad {weighed}\quad {out}\quad (g)}$

[0188] The result is always given with the amount weighed out.

[0189] The Use of Silicas According to the Invention in Lacquers.

[0190] Silicas according to the invention in accordance with examples 1to 7 are tested in various lacquer systems. The results of these testsare given in Tables 5 to 8.

[0191] Table 5 shows the effect of silicas according to the invention inaccordance with examples 1 to 7 which are used in black stoving lacquerDUPLEX D 1326 and this is compared with the matting agent in accordancewith DE 24 14 478.

[0192] The stoving lacquer DUPLEX 1326 is a commercial product fromDuPont Coatings, Austria. The basis of the binder is an alkyd/melamineresin. Characteristics: black pigmented alkyl/melamine resin stovinglacquer, high-gloss, original use: motor vehicle (HGV) mass productionlacquer. It is used as a standard test system, in particular for testingthe grindometer value and the matting efficiency.

[0193] It is used as a model for pigmented industrial lacquers withaverage mattability. An identical gloss level (60° reflectometer value)was set for all the products by varying the amount weighed out.

[0194] The Results are as Follows:

[0195] It is obvious from the values in the Table that, despite thepresence of a coating and lower grindometer values (particle size), noimpairment to the high matting effect is demonstrated.

[0196] Table 6 shows the effect of silicas according to the invention inaccordance with examples 1 to 7 which are used in a NC test lacquer forsuspended particle tests and this is compared with the matting agent inaccordance with DE 24 14 478. The NC test lacquer is used exclusivelyfor testing the settling out behavior of matting agents. It has thefollowing composition. Raw material Concentration Amount Toluene 15.00Butanol 10.00 Ethyl acetate 10.00 Butyl acetate 85 10.00 NC-Chips E 51082/18 DBP 12.00 Dibutyl phthalate 1.00 Castor oil 18 P aerated 2.00Jagalyd E 42 60.00% in xylene 10.00 Alresat KM 31 50.00% in ethylacetate/butyl 20.00 1:1 acetate 85% Petrol 100/140 10.00 Total 100.00

[0197] The Results are as Follows:

[0198] Almost all the coated samples have greatly improved suspendedparticle behavior. Sometimes, no settling out at all is observed(examples 3 and 4).

[0199] Table 7 shows the effect of silicas according to the invention inaccordance with examples 1 to 7 which are used in DD blue-streak lacquerP and this is compared with the matting agent in accordance with DE 2414 478. The blue-streak lacquer is a 2-component polyurethane lacquerand is used in particular to test matting efficiency. It is used as amodel for unpigmented wood and furniture lacquers which are difficult toprovide with a matt finish. The direct effect of the matting agent onthe degree of gloss (reflectometer value) is obtained by always weighingout the same amount of all the products.

[0200] The blue-streak lacquer has the following composition: Rawmaterial Concentration Amount Butyl acetate 98% 8.30 Ethoxypropylacetate 16.50 Desmophen 800 115.00 Desmophen 1100 20.00 CAB 381-0.510.00% in butyl acetate 98% 3.00 Mowilith 20 50.00% in ethyl acetate3.00 Baysilone OL 10.00 in xylene 0.10 BYK 361 0.30 Xylene 33.80 Total100.00

[0201] The Results are as Follows:

[0202] All the samples have a low thixotropy and only a small or zerorheological effect on the lacquer system. This has an advantageouseffect on the lacquer processing properties.

[0203] Table 8 shows the effect of silicas according to the invention inaccordance with examples 1 to 7 in the standardized wax detachment test.This test is used to check whether all the coating agent applied toprevent settling out remains on the silica in the lacquer and cannot beremoved. For this purpose, the coated silicas are subjected to storagein ethoxypropyl acetate at elevated temperature. If a product passesthis test, it can be predicted with high probability that the resultwill apply in all lacquer systems.

[0204] The results show that detachment of the coating agent cannot bedetected with any of these silicas. TABLE 5 Dispersion: 10 min bladeagitator, Ø 45 mm 2000 rpm PE beaker 350 ml A B C D E F G H I J Stovinglacquer black 100 100 100 100 100 100 100 100 100 100 DUBLEX D 1326 gDilution V 0003 g 20 20 20 20 20 20 20 20 20 20 ACEMATT TS 100 g 2.4Example 1 g 2.6 Example 2 g 2.6 Example 3 g 2.7 Example 4 g 2.9 Example5 g 2.7 Example 6 g 3.4 Example 7 g 2.4 ACEMATT OK 500 g 3.8 ACEMATT OK520 g 4.1 Discharge time DIN beaker 4 mm s 30 32 30 33 34 34 30 26 31Grindometer value μm 42 40 40 39 38 40 40 26 28 Specks up to μm not — —— — — — — — — clean Application using film applicator Erichsen 509 MC onglass discs, rate of application 25 mm/s, slot spreader 120 μm, dryingtime: 10-20 min, stoving conditions: 20 min 150° C. Air temperaturewhile drying ° C. 23 23 23 23 23 23 23 23 23 23 Relative humidity whiledrying % 70 70 70 70 70 70 70 70 70 70 Thickness of layer μm 24 24 24 2424 24 24 24 24 24 60°-Reflectometer value 36.6 35.4 37.4 37.5 35.2 37.236.7 37.9 35.5 35.7 85°-Reflectometer value 71.7 71.8 74.1 71.6 69.169.4 72.0 72.1 83.6 83.6 Δ85°-60° Reflectometer value 35.1 36.4 36.734.1 33.9 32.2 35.3 34.2 48.1 47.9

[0205] TABLE 6 Dispersion: 10 min blade agitator, Ø 45 mm 2000 U/min PEbeaker 350 ml A B C D E F G H NC test lacquer for suspended particlestest g 40.0 40.0 40.0 40.0 40.0 40.0 40.0 40.0 ACEMATT TS 100 g  0.4Example 1 g  0.4 Example 2 g  0.4 Example 3 g  0.4 Example 4 g  0.4Example 5 g  0.4 Example 6 g  0.4 Example 7 g  0.4 g 40.4 40.4 40.4 40.440.4 40.4 40.4 40.4 Quality of sediment (Scale 1-5) 1 = no separation oflacquer and MM X X 2 = fluffy sediment X X X X 3 = soft sediment 4 =soft sediment/difficult to stir X 5 = solid sediment X Testing thesuspended solids behavior 10 days in drying cabinet (+50°) 14 hourscentrifuge, Jouan CT 4.22 X X X X X X X X

[0206] TABLE 7 Dispersion: 10 min blade agitator, Ø 45 mm 2000 U/min PEbeaker 350 ml A B C D E F G H DD blue-streak lacquer g 100 100 100 100100 100 100 ACEMATT TS 100 g 4.4 Example 1 g 4.4 Example 2 g 4.4 Example3 g 4.4 Example 4 g 4.4 Example 5 g 4.4 Example 6 g 4.4 Example 7 gDischarge time cog - beaker 4 mm s ca 24 ca 20 ca 19 14 13 18 11Addition of Desmodur L 75 K g 50 50 50 50 50 50 50 Discharge time cog -beaker 4 mm s 16 16 15 13 13 16 12 Knife application to black discs,slot spreader 150 μm, Coatmaster 509 MC, 25 mm/s, drying time: 25-30min, forced drying 120 min 50° C. Temperature during application ° C. 2222 22 22 22 22 22 Rel. humidity during application % 55 55 55 55 55 5555 Thickness of layer, μm 60°-Reflectometer value 16.5 21.5 28.0 25.430.0 25.3 83.6 85°-Reflectometer value 41.7 50.3 56.7 55.5 62.1 57.091.3 Δ85°-60° Reflectometer value 25.2 28.8 28.7 30.1 32.1 31.7 7.7Density with yellow filter over black surface

[0207] TABLE 8 Sample Wax no. Name of sample detachment Comments AACEMATT TS 100 No Uncoated standard B Example 1 No C Example 2 No DExample 3 No E Example 4 No F Example 5 No G Example 6 No H Example 7 No

1. A structurally coated silica.
 2. A structurally coated silica asclaimed in claim 1, wherein it has a carbon content of 10 to 30 wt. %.3. A structurally coated silica as claimed in claim 1, wherein it has aBET surface area of 80 to 450 m²/g.
 4. A structurally coated silica asclaimed in claims 1 or 2, wherein it has a bulk density of 10 to 60 g/l.5. A structurally coated silica as claimed in claims 1 to 3, wherein ithas a DBP index of 2.4 to 3.8.
 6. A process for preparing a structurallycoated silica as claimed in claims 1 to 4, wherein a pyrogenic silica issprayed and mixed with water and a coating agent in a suitable mixingvessel and is then milled and subsequently dried.
 7. Use of structurallycoated silicas as claimed in claims 1 to 4 as matting agents inlacquers.
 8. Lacquers and/or lacquer systems, wherein they contain astructurally coated silica as claimed in claims 1 to 4.